According to Einstein's theories of relativity, the mass of Earth dimples space-time like a heavy person sitting in the middle of a trampoline. (NASA)

A NASA probe circling the Earth has found evidence that confirms two key predictions based on Albert Einstein's theory of general relativity.

The results from the Gravity Probe B mission show that the Earth's mass does warp space and time, which are interlinked, NASA announced Wednesday.

They also confirm that the Earth does drag space-time with it as it rotates, as predicted.

"Imagine the Earth as if it were immersed in honey. As the planet rotates, the honey around it would swirl, and it's the same with space and time," Francis Everitt, the Stanford University physicist who led the mission, said in a statement.

The results are published in the journal Physical Review Letters.

Space-time and relativity

German-American physicist Albert Einstein's theories of special relativity and general relativity say that space and time are woven together into four-dimensional "space-time." The mass of Earth dimples this "fabric" like a heavy person sitting in the middle of a trampoline. Gravity results from the tendency of other masses to follow the curve of space-time and roll into the dimple. The theories predict that as the Earth spins, it should twist the dimple Ã¢ÂÂ" an effect that should be measurable using precise gyroscopes.

Gravity Probe B was designed to test the predictions by taking measurements from four ultra-precise gyroscopes. Those instruments contain rotors that NASA bills as the "most perfect spheres ever made by humans," allowing them to spin indefinitely without drifting from the alignment of their rotation.

The gyroscopes were aboard a spacecraft circling the Earth in a polar orbit Ã¢ÂÂ" that is, it travelled perpendicular to the Earth's rotation, passing over both poles during each orbit.

The experiment was set up so the gyroscopes' axes of rotation should always point in the same direction Ã¢ÂÂ" toward the "guide" star IM Pegasi Ã¢ÂÂ" provided the Earth's gravity did not affect space and time.

However, the researchers detected tiny, measurable changes in the direction of the gyroscopes' spins, confirming that the Earth's gravity does:

Warp space and time around it, which is called the geodetic effect.

Pull space and time with it as it rotates, an effect called frame dragging.

NASA began planning the mission in 1963, making it one of the longest-running projects in the U.S. space agency's history. The satellite was decommissioned in December 2010, after the final parcels of data were collected.